| 1. |
- Degago, S. A., et al.
(författare)
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Time- and stress-compressibility of clays during primary consolidation
- 2010
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Ingår i: Numerical Methods in Geotechnical Engineering - Proceedings of the 7th European Conference on Numerical Methods in Geotechnical Engineering, NUMGE 2010, Trondheim, Norway, 2-4 June 2010. - : CRC Press. - 9780415592390 ; , s. 125-130
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Konferensbidrag (refereegranskat)abstract
- The existence of creep deformation during primary consolidation has been widely accepted; however, there are still contradicting opinions on the mechanisms that govern creep during the primary consolidation phase. This study aims to assess creep effects during primary consolidation such that it is possible to critically evaluate and challenge some of these opinions. A special type of interconnected oedometer tests were designed and conducted. The tests were numerically studied using a soil model based on the isotache concept. These analyses show that the isotache concept can capture the important features of the tests well and thereby describe the time- and stress-compressibility of a soil during the entire soil compression phase.
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| 2. |
- Degago, S.A., et al.
(författare)
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Use and misuse of the isotache concept with respect to creep hypotheses A and B
- 2011
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Ingår i: Geotechnique. - 0016-8505 .- 1751-7656. ; 61:10, s. 897-908
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Tidskriftsartikel (refereegranskat)abstract
- Time-dependent settlements of thick in situ clay layers are normally analysed based on results of thin laboratory specimens. However, the time used to complete primary consolidation is significantly different for laboratory specimens and in situ soil layers. Two totally different cases, referred to as creep hypotheses A and B, have been used as a basis of discussion to assess the effect of creep during the primary consolidation phase. Several laboratory and field experiments have been conducted to study the effect of soil layer thickness on the time-dependent compressibility of a soil layer. Some of these tests seemed to support hypothesis A, others hypothesis B, and in some cases showed a behaviour between the two. As a result this question has continued to be a controversial topic among researchers, and remains to be an issue that needs to be resolved. In this study, some relevant experimental investigations from the literature are thoroughly studied and critically reviewed, and also explained consistently using the isotache concept. This work indicates that the isotache approach can capture the main characteristics of the time-dependent compressibility of clays during both the primary and secondary consolidation phases. It is also shown that the misuse of the isotache concept, as reported in the literature, may give a confusing picture of reality. Based on the considered data, it is demonstrated that the measured time-dependent compressibility of clays agrees well with hypothesis B.
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| 3. |
- Grimstad, G., et al.
(författare)
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Modeling creep and rate effects in structured anisotropic soft clays
- 2010
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Ingår i: Acta Geotechnica. ; 5:1, s. 69-81
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Tidskriftsartikel (refereegranskat)abstract
- In simulations of undrained triaxial tests, most soil models fail to capture the effect of post peak strain rate variation. This is due to the fact that no "swelling" is allowed for the viscoplastic volume strain. Imposing such restriction implies that dilative behavior cannot be modeled. Therefore, a model incorporating creep has been formulated using the so-called time resistance concept that uses a single creep parameter determined from an incremental oedometer test. The key feature of the proposed model is the introduction of the time resistance concept on the plastic multiplier rather than on the volumetric viscoplastic strain. This allows the viscoplastic volume strain to be either positive or negative depending on whether the state of the soil is on the "wet" or "dry" side of critical state line. The proposed model is based on an existing elastoplastic model for structured soft clay (S-CLAY1S). The paper gives a description of the constitutive model and the numerical scheme used in the implementation of the model. Capabilities of the model are illustrated with simulations of oedometer and triaxial tests. Results from such analyses show that the model is able to capture essential features of soft clay behavior.
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